I have to assume you are talking within the compilation of final fantasy vii.
Yes, it would appear that there was indeed a child named sephiroth, as he is about 30 years old, and he was born in the normal fashion, even if his conception and development was less than immaculate. One can assume that lucrecia chose the name. Sephiroth's childhood, however, is completly unknown. He was the first SOLDIER, but whether this was something he began at an early age or not is a mystery. We do not even know who raised him, although there it could have been hojo.Xoxosephiroth-YES OF COURSE.
- It's more likely that Hojo chose the name. He took Sephiroth away right after he was born. Besides that, there's the fact that he has no surname, almost like "Sephiroth" is a label for an experiment. Finally--although this may not count, because there's no guarantee real world symbolism applies to FFVII's world--there's the meaning of the word "Sephiroth." I don't think that Lucretia was quite arrogant enough to name her child "the aspects through which God manifests in the world," but that was essentially what the Jenova Project was going for.